Cal Poly Receives Grant to Develop Improved Desalination Technology

SAN LUIS OBISPO — Cal Poly chemistry Professor Shanju Zhang received a $300,000 grant from the National Science Foundation to use nanotechnology to improve desalination techniques by using far less energy than traditional methods.

Currently, water is desalinated by pushing it through an osmosis membrane, which requires a great deal of pressure and, therefore, a lot of energy. With California’s ongoing drought, this new technology could provide long-term relief for the Golden State and beyond. Although a strong El Nino is expected to bring much-needed rainfall to the state this year, experts predict it might not be enough to erase four record dry-years.

Zhang and a group of students are experimenting with integrating a layer of carbon nanotubes into a desalination membrane, which would change the way the water flows.

Because water flows through nanotubes much faster than it flows outside of them — up to a million times faster — the speed of the water moving through the tubes provides the necessary pressure. Large molecules, such as salt, are too big to fit into the tubes and so will not pass through the membrane.

“These new materials will reduce the cost of water purification and improve efficiency,” Zhang said.

The key to making the nanotubes filter water is to align them vertically. To achieve this, Zhang and his students have developed a liquid crystalline polymer that holds the nanotubes and serves as the desalination membrane. Through an interdisciplinary collaboration with Xiaoying Rong, a faculty member in Cal Poly’s Graphic Communication Department, the team then prints the liquid crystal onto a substrate, similar to the way ink is printed onto paper. Because of the printing method and the qualities of the polymer, the nanotubes align.

Zhang’s students have been involved in the real-world research project from day one. “Students make the materials, use advanced instruments, and print the film. They learn a lot of lab and problem-solving skills they can't learn from a textbook. Those are real skills for the future,” Zhang said.

“My research with Dr. Zhang gives me the freedom to approach problems without following a lab manual,” said Evan Scherzinger, who presented the research team’s findings at the Western Coatings Symposium in Las Vegas in fall 2015. “This ability makes me a much better chemist and prepares me for the challenges I'll face in industry.”